<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .border {
	margin: 300px auto;
	width: 200px;
	height: 100px;
    line-height: 100px;
    text-align: center;
	background: 
        linear-gradient(blue, blue) left top,
		linear-gradient(blue, blue) left top,
		linear-gradient(blue, blue) right top,
		linear-gradient(blue, blue) right top,
		linear-gradient(blue, blue) left bottom,
		linear-gradient(blue, blue) left bottom,
		linear-gradient(blue, blue) right bottom,
		linear-gradient(blue, blue) right bottom;
	background-repeat: no-repeat;
	background-size: 1px 24px, 24px 1px;
    background-color: aquamarine;
}
    </style>
</head>
<body>
    <div class="border">
            123456
    </div>
</body>
</html>